Aldimines



Patented Jan. 8, 1952 UNITED sTATEs PATENT, OFFICE p ALDIM INES Melvin D, Hu'rwitz, Philadelphia, Pa., assignor to .Rohm "&' Haas Compan corporation of Delaware Application February 11, 1950b .Serial Nfi'fl43,834

' Tommi, (o1. 260--566) No Drawing.

of the secondary products are unusually high:

Thus, for example, they can be hydrogenated and thus converted into new classes of secondaryaminescontaining tertiarycarbon atoms.

I All of the products of this invention contain the molecular configuration I Wherein-C -is a tertiary carbonatom connected to three other carbon atoms and all of the compounds are made by reacting a compound containing an aldehyde group, -CHO, with a compound containing a primary amino group, NH2,

tic groupings.

y, Philadelphia, Pa., a.

are each attached to tertiary carbon atoms. Furthermore, when a dia'ldehyde is reacted with a diamine in which the amino groups are on ter-= tiary carbon atoms a linear polymer is formedwhich contains a large number of the characteris- Such resins are new and have real value. a

a tertiary carbon atom.

' hydrogen atom. Furthermore, R and R taken uent R and is attached directly to the nitrogen atom by the carbon atom which carries R This type of aldimine is prepared according to the attached to atertiary carbon atom. The re- =1 action can be appreciated from the following v representation of the course of the reaction;

lLtI-NHZ -o J J N=CH- mo I I v g The largest class of the aldimines of this in- ,ventionare those prepared from monoamines and monoaldehydes and which therefore con-- tain one of the characteristic configurations As indicated above. the simplest class of these new aldimines includes those made from one mole of amonoaldehyde and one mole of a primary amine containing'an amino group attached to Such aldimines or Schiff's bases have the general formula in which R R and R represent inonovalent organic radicals, preferably hydrocarbon radilcals, and in which R is a monovalent organic radical, preferably a hydrocarbon radical or a together with the tertiary carbon atom can representan aliphatic, cyclic, radical such as the cyclohexyl radical which carries the substitfollowing equation by reacting a monoaldehydo compound of the general formula RCHO with a monoamine having the general formula 1 in whichformulas the Rs havethe same signifishown above; But there are other new aldimineswhich contain a plurality of such configurations;

Thus when a mole of a dialdehyde such as glyoxal is reacted with two molesof a tertiary alkyl' amine the product contains twogroupings. Two such groupings are also present,

; in the products made from two moles of a mono aldehyde and one mole of a diamine such as 6.1- aminomenthane in-which the two amino groups canoe as is described above:

R Rx

Careful study hasshown that the groups or radicals which are represented by the four Rs'remain-intact during the reaction and that the U reaction does in fact take the course shown in the equationr -When a mole of a dialdehydo compound reacts with two moles of an amine the reaction takes the course which is shown in this equation:

7 a v 2 R-NH: oac-a cno R1 f R1 3 in which R R and R have the significance described above, and R is a divalent organic radical, preferably a hydrocarbon radical. The prod nets are bis-Schiffs bases.

The reaction of a monoaldehyde and a diamine in which both of the amino groups are attached to tertiary carbon atoms is best illustrated by the reaction between diaminomenthane and benzaldehyde:

CH3 CH:

- Examples of operable monoaldehydes which give rise to the =CI-IR portion of the aldimines shown above includes formaldehyde; in which the group corresponding to R in the general formulas is a hydrogen atom, and the following aldehydes in which the groups represented by R are monovalent organic radicals, preferably hydrocarbon radicals: acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde, methylethylacetaldehyde, n-valeraldehyde, trimethylacetaldehyde, heptaldehyde, caprylaldehyde, pelargonic aldehyde, stearic aldehyde, acrolein, cro-' tonaldehyde, vinylacetaldehyde, a-methylcrotonaldehyde, e-methylcrotonaldehyde, a,,3-dimethylcrotonaldehyde, 11,5 diethylcrotonaldehyde, citronellal, benzaldehyde, salicylaldehyde, m-nitrobenzaldehyde, pechlorobenzaldehyde, phenylacetaldehyde, cinnamic' aldehyde, fur'fural'dehyde,"

thiophenealdehyde, hexahydrobenzaldehyde, tetrahydrobenzaldehyde, tetrahydrotolualdehydes (0-, mand p-) aand ,B-naphthaldehydes, and

tertiary carbon: atom; The preferred class of amines is made up of those individuals-which have three monovalent hydrocarbon radicals attached to the tertiary carbon atom. That is, the preferred class of amines includes those amines in which the groups represented by R R. and

R. in the general-formulas aboveare monovalent hydrocarbon radicals. cals, which are represented byR R and R can be alkyl, aryl, alkaryl, aralkyl 0r cycloalkyl groups. terest and utility are those in which the total number of carbon atoms in the groups 'repre- These hydrocarbon radi The aldimines of greatesteurrent in-' of monoamines which are operable in the preparation of the aldimines of this invention includes those in which the tertiary carbon atom, shown as or C in the above formulas, and two of the R- groups, say R and R all taken together form an aliphatic ring, to one and the same carbon atom of which are attached both the primary amino group and the monovalent radical represented by R That is to say, R and R can represent an alkylene group, preferably a polymethylene group, the terminal carbon atoms of which are attached to the tertiary carbon atom which carries the radical represented by R. Examples of such amines are the following:

' GET-OH: v

/CNH2 112-011: cm

CHr-CHn C52 G NH2 CHr Cfiz GzH;

pom-0H: e o nm CHg Cfig (EH1 and the like.

Mixtures of I the amines describedabove, par- 1 ticularly mixtures of isomeric amines, can be reacted with an aldehyde to produce a mixture.

of new-Schiffs bases.

Diamines which react with monoaldehydes or dialdehydes to produce new aldimines and in which the two amino groups are attached to tertiary carbon atoms are exemplified by diaminomenthane, the formula of which is shown above, and 2,5-dimethyl-2,5-diaminohexane of the formula,

The reaction by which the new aldimines are produced takes place readily. Temperatures from 10 C. to 250 C. have been employed successfully at atmospheric pressure. At the very low temperatures it is advisable to employ amaterial such as solid potassium hydroxide, for

example, to take up the water of reaction so that the reaction may .proceed to completion. In the such .as fu-rfuraldehyde, however, temperatures up to the boiling pointof the aldimine are satisfactory. Ordinarily catalysts are not required since the reaction of aldehyde and amine takes place readily. In some instances, the addition of a small amount-ofacid is advantageous in accelerating the reaction. The amines and the sented by R R and R? is eighteen or less. The

minimum number of course is three when R R. and It all represent methyl groups. Suitable hydrocarbon radicals are exemplified by'the fol lowing: methyl, ethyl, isopropyl, tert.-butyl, sec.- amyl, 2-ethylhexyl, lauryl, hexadecyl groups and any isomers of these, groups; and phenyl, benzyl, p-tert.-amyl and naphthyl groups. Another class aldehydes react in the ratio of one mole of amine to each'aldehydo-group in a mole of aldehyde but it is evident that an excess of either can be used if desired. As indicated above, these new 'Schiff's bases are unusually .stable. As a result,

they can be separated without difliculty from the reaction mixture or from an excess of either reactants, and can bepurified by distillatiomprefr jblyundergeducedipressure- H I The products of thisdnve'ntion are monomeric; f This is, speciallysurprisingin the case of the since the literature teaches that primary amines and formaldehyde give cyclic, trimeric" Schifis' bases" as the only stableproducts.

The following examples serve to illustrate how the products of this invention can be made.

Example. 1

Ina flask, equipped with a reflux condenser,-

thermometer .and mechanical stirrer was placed 73 parts of tert.-butyl amine. To this was added with stirring 81 parts of 37% aqueous formaldehyde. The'temperature rose spontaneously and the flask was cooled to prevent refluxing. The mixture was stirred for an additional half hour and was then cooled to room temperature. The organic material was separated from the heavier water layer and was'dried over pellets of potassium hydroxide. The aqueous layer was found to contain less than 1% formaldehyde. It was then distilled through a short packed column at a rate such that the-temperature ofthe vapor did not rise above 65 C., although the pot temperature varied between 112 and 118 C. The

yield of 60 parts represented a 70% yield of tert butyl azomethine having a boiling point of 53- 65. 0., a neutral equivalent of 8'7 (asLagai-nst a calculated value of 85) (CH3)3CN=CH2. (The neutral equivalent is determined by the conventional method of titrating the product with 0.5 N sulfuric acid to a bromocresol green endpoint.)

Example 2 By the same procedure as that employed in Example 1, 87 parts of 37% aqueous formaldeformula The product had a neutral equivalent of 1&0 "as against a calculated value of 141 and on analysis it was found to contain the following: 76.32% carbon, 14.0% hydrogen, 10.22% nitrogen as and the formula against the following calculated values: 77.55%

carbon, 13.5% hydrogen and 9.95% nitrogen.

In another reaction, an equivalent amount of paraformaldehyde was employed in place of the formaldehyde. While the product was identical to that of Example 2, the rate of reaction was much slower. 7

' Example 3 In the mannerdescribed above, 81 parts of aqueous formaldehyde and 185 parts of tert.

dddecylamine (isoheptyldiethylcarbinylamine) were reacted. The organic layer was treated as described above and a yield of 185 parts of tort.-

dodecylazomethine was obtained which boiled.

over the range to C. at 10 mm. of pressure (Hg) and, had a: neutral equivalent of 199.as.. against a calculated value ofl 197.. ."v The 'anals.

ysis oi -the"product-confirmed that it had the" formula By the same procedure 81 parts of 37% aqueous formaldehyde was added to and reacted with 213 parts of tert.-tetradecylamine .(octylethylpropylcarbinylamine I 'csrnaozne (can-00 mm) As in ;a1l cases, the reaction was exothermic and" was collected within the boiling range of 156 to CsH17 (CzI-Is) (C3H7)'CN=CH2 Example 5 To 5.9 parts'of 37% aqueous formaldehyde was added 6.75 partsof a,a-dimethylbenzylamine and The reaction mixture was then extracted with benthe mixture was shaken for five minutes.

zene and the benzene solution was then fractionally distilled. Six partsv of a fraction was collected at 92-95 C. andlO mm. of pressure (Hg). Its neutral equivalent was found to be as against a calculated value of 147 for the compound having this formula:

Example 6 A mixture of 9.0 parts of a 37% aqueoussolution of formaldehyde and 8.45 parts of 1,8-. diamino-p-menthane was shaken for 5 minutes.

The water was then removed by the addition of pellets of potassium hydroxide and the dried organic material was distilled. Nine and onehalf parts of p-menthane bis(azomethine) was c0llected.- This product boiled at 115120 C. at 10 mm. of pressure and had a neutral equivalent of 95 as against a calculated value of 97 for the compound having this formula:

A mixturewas made of 194 parts of a 30% aqueous solution. of glyoxal and 258 parts of neopentyldimethylcarbinylamine and the mixture was stirred for 0.5 hour. exothermic. andZi-TdistiIled under yacuum and the fraction In the next ex- The reaction was The organic layer was separated m l sa 8 9-90" i -.and '1 .:mm.:0tpressure was:

collected. This material had an analysis-which agreed with that calculated for the bis(azomethine) having the formula:

To 129 parts of neopentyldimethylcarbinyl amine and 50 parts of toluene was added 96 parts of furfural. The temperature of the mixture rose spontaneously and water separated. The mixture was refluxed and the water which vapor-- ized with the toluene was removed by means of a continuous separator. When 18 parts of water had been thus removed, the reaction mixture was distilled and the compound having the formula and boiling at 138-141 C. and 30 mm. of pressure was obtained in a. 97% yield.

Example 9 In a'modification of the process of Example 8,

a mixture of 142. parts of neopentyldimethyl-' carbinylamine and 96 parts of 'furfuraldehyde was simply distilled to a pot temperature of 250 C. The

residue was then distilled under reduced pres-" sure and there was'obtained a 93% yield of furfurylidene neopentyldimethylcarbinylamine, identical with the product of Example 8.

Example 10 To 142 parts of neopentyldimethylcarbinylamine and 150 parts of benzene was added '70 parts of crotonaldehyde. The mixture was heated and the water was removed as described in Example 8. The pot temperature never exceeded 105 C. r The reaction mixture was then distilled under reduced pressure and a water- White liquid which boiled at l08-lll C. was obtained in an 89% yield. The analysis of the product confirmed that the formula was the following:

CH1 H3 By the process of Example 10, 142 parts of neopentyldimethylcarbinylamine and 72 parts of n-butyraldehyde were reacted in the presence of 150 parts of benzene. The product having the and boiling at 60'-C.and 2.5 'mm. of pressure wasobtained in-a 93 yield. 1

Example 12 By the procedure of Example 8, 129 parts of neopentyldimethylcarbinylamine and 126 parts of a-ethyl-p-propylacrolein were reacted to give 1 an 82% yield of a product; boiling at 141-148 C.

at'l'l'mm. whose analysis was that of therein v pound (cmnccmcwmml-cnckclnn acmcznu ture.

;--,mixture was then distilled under reduced --Example13 The process of Example 8 was followed in re acting 142 parts of 3,5,5-trimethylhexanal and 129 parts of neopentyldimethylcarbinylamine.

" The product, which boiled at 8094 C. at 0.2 mm.

or pressure, represented an 82% yield of (CHJ)3CCH2C(CH3)a-N= CHCHaCI-I (CH3) CHzC (CH3 3 Example 14 A mixture of 106 parts of benzaldehyde and 129 parts of neopentyldimethylcarbinylamine was allowed to stand overnight at room temperatained of the compound (CH3 3CCH2C(CH3) 2N=CHC6H5 which boiled at 1'29- -131 C. and 8 mm. of pressure.

Example 1 6 To 73 parts of trt-butylamine there was added dropwise '72 parts of n-butyraldehyde while the temperature was maintained at -5 C.

Solid-potassium hydroxide was then added in order to take up the water of reaction. After an hour the reaction mixture was distilled under reduced pressure and the product which boiled at C. and 20 mm. of pressure, was obtained in a 92% yield.

Example 17 A yield of (CH3)3C-N=CHCH3 was obtained by reacting '44 parts of acetaldehyde and 73 parts of tert.-butylamine by the process of EX- ample 16 and thereafter distilling the product.

Example 18 A mixture of 106 parts of benzaldehyde and 73 parts of tert.butylamine was allow to stand overnight at room temperature. The. reaction sure and a 63 yield of the compound (CH3 3C-N=CHC6H5 was obtained.

Example 19 To a mixture or 101 parts of a mixture of hexylamines (containing approximately '40 methyldiethylcarbinylamine, 45% dimethylpropylcarbinylamine and 15 dimethylisopropylcarbinylamine) was added 73 parts of isobutyraldehyde while the temperature was maintained below 50 C. The mixture was treated with 8 parts of solid potassium hydroxide below 30 C. and after an hour the organic layer was separated and distilled under reduced pressure. The fraction boiling at 759- C. and 25 mm. of pressure was a water-white liquid whose analysis corresponded to that calculated for a'compound of the empiri- 'cal formula CwHnN. v

v The reaction mixture was then distilled under reduced pressure and a 78% yield was ob- To 113 parts of l-methyl l-aminocyclohexane was added 96 parts of furfural'. reaction occurred which carried the temperature to 65 C. Potassiumcarbonate was added in order to salt out the water and the organic layer was then dried over potassium carbonate An exothermic.

and finally distilled under reduced pressure. The

product boiled at 125-l35 C. at30 mm. of pres-j sure and had aneutral equivalent of 192 as against a theoretical value of 191 for the compound a on;

While the temperature was maintained below 35 C. by means of external cooling, 97 parts of a 30% aqueous solution of glyoxal was added with stirring to 80 parts of tertJ-butylamine.

mixture was then allowed to stand overnight at" room temperature. The mixture was next saturated with solid potassium carbonate and the organic layer which separated was removed and dried over potassium carbonate. The dried product was distilled under reduced pressure to give a bis-Schiffs base of the formula which boiled at 80-90 C.'at mm. of pressure.

Example 22 The procedure of Example 21 was followed with one exception namely that 150 parts of neopen- Example 26 Terephthalaldehyde (-13.4 parts) was mixed with 100 parts (a large excess) of neopentyldimethylcarbinylamine. The reaction mixture was heated to'refiux and 355 parts of water was removed az'eotrop-ically. The mixture was then cooled and 30 parts of a compound crystallized from the excess of amine solvent. This compound had a melting oint of 84-85 C.

Example 27 42.6 parts of the dialdehyde, obtained by the esterification of ethylene glycol with a-ethyl-aaldehydo-octoic acid, was mixed with 26 parts of neopentyldimethylcarbinylamine. The mixture was warmed and water separated. Fifty parts of toluene was added and the water was removed azeotropically. The mixture was then stripped to 150 C. and 1 mm. to yield an amber tyldimethylcarbinylamine was substitutedfor the tert.-butylamine. and 1 mm. of pressure and its analysis corresponded to that calculated .for the bis-Schifis base of the formula The product boiled at 90" C.

Example 23 The procedure of Example 21 was followed in reacting 135 parts of a,a-dimethylbenzylamine with 97 parts of a 30% aqueous solution of glyoxal and in isolating the product. The material which boiled at 180-200 C. and 1 mm. of pressure had the formula CeH5C (CH2) --N=CHCH=NC(CH2) CsHs as evidenced by analysis.

Example 24 To 20 parts of tert.-butylamine dissolved in 30 parts of benzene was slowly added 17.2 parts of 2,4-dimethyl-2-methoxy methylglutaric aldehyde. The mixture was then maintained at 50 C. for 4 hours after which it was stripped to 100 C. at 15 mm. of pressure to free it of benzene, water and. excess amine. The liquid residue had a neutral equivalent of 149' as against a value of 141, calculated for the compound having the formula CH3 CH: 2 (CH )aCN=CH-CCHCHCH=N-C(CH3):

moon; I l Example 25 Seventeen parts of freshly distilled sebacic viscous liquid whose analysis agreed with that calculated for the compound having the formula Example 28 A mixture of 9.0 parts ofa 37% aqueous solu- -tion of formaldehyde and 7.2 parts of 2,5-diamino-2,5-dimethylhexane was shaken for 5 minutes. The water was then removed by the additlon of pellets of potassium hydroxide and the dried organic material was distilled. Seven and .a half parts of product was obtained which boiled at -100 C. and 25 mm. of pressure. It had a neutral equivalent of 88 (as against a calculated value of 84) and its analysis confirmed this formula:

' cm on,

oHz=N- omoHz-e-N=om E.'t'ample 29 To 85 parts of 1,8-diamino-p-menthane, dissolvedin'100 parts of toluene, was added 142 parts of 3,5,5-trimethylhexanal. The reaction mixture was heated to reflux and 13 parts of -water was removedazeotropically. The reaction mixture was stripped to a final pot temperature of C. at 1 mm. of pressure and 203 parts of a pale yellow liquid remained as residue. This product had a neutral equivalent of 216 (calculated=20 9) and analysis showed the compound to have the structure .CH: CH2-CH2 CH3 CH3 C-rN=OHCH2H-CH2C (CH3)3 Examples 30-32 The procedure of Example 29 was followed in reacting 96 parts of furfural, 126 parts of 2- ethylhexanal and 106 parts of benzaldehyde respectively with 85 parts of 1,8-diaminop-menthane. In every instance analysis of the resulting liquid products corresponded respectively to the formulas shown below and yields of at least 92% were obtained:

Forty-four parts of acetal'dehyde'was added dropwise to 85 grams of 1,8-diamino-p-menthane while the temperature was held below C. by means of an ice-salt bath and the mixture was held at 5 C. for four hours. The reaction mixture was then saturated with solid potassium hydroxide and the organic layer was dried over. potassium hydroxide. The product was then distilled at 1 mm. of pressure and a water-white liquid which boiled at l0O-110 C. and 1. mm. was obtained which analysis showed to have the following formula:

3H3 GET-0H, von. OH3CH=NCCH CN=CHCH;

H; ore-om Iclaim: 1. A process for making azomethines having the general formula 31 R -c -N='c'H,

in which R R and R represent alkyl groups, WhlCh process comprises reacting 'equimolar amounts of formaldehyde and a primary amine having the general formula 1 12 in which R, R and :R are identical with the same characters described above.

3. A process for making the azomethine of the formula which comprises reacting equimolar amounts of formaldehyde and the amine of the formula 4. A process for making the azomethine of the formula which comprises reacting equimolar amounts of formaldehyde and tertiary-butylamine.

5.. A process. for making the azomethine of the formula which comprises reacting equimolar amounts of formaldehyde and the amine of the formula 6. A process for making the azomethine of the formula which comprises reacting equimolar amounts of formaldehyde and the amine of the formula CH:CHi-CNH:

7. A process for making the'azomethine of the formula 5 which comprises reacting equimolar amounts of Y formaldehyde and the. amine of the formula CH; C.H',,- JNH,

MELVIN D. I-IURWITZ.

REFERENCES CITED Thefollowing references are of record in the file a: this patent:

UNITED STATES PATENTS Number Name Date 2,421,937 Haury June 10, 1947 2,468,593 Dorman Apr. 26, 1949 

1. A PROCESS FOR MAKING AZOMETHINES HAVING THE GENERAL FORMULA 